- Last Update On : 2013-03-02
Polycythemia or erythrocytosis may be defined as an elevation of the hemoglobin or hematocrit. The primary objective in the laboratory evaluation of polycythemia is to determine whether polycythemia vera is present, and to distinguish it from relative polycythemia (an elevated hemoglobin secondary to plasma volume depletion, with normal red cell mass), and secondary erythrocytosis (erythropoietin-mediated increase in red cells). Traditionally, this work-up has included the laboratory measurement of red cell mass. In fact, demonstration of an increased red cell mass was included in the diagnostic criteria for polycythemia vera established by the Polycythemia Vera Study Group 25 years ago.
Measurement of red cell mass is expensive, time-consuming and cumbersome. Recently, it has become evident that this procedure may not always be necessary or reliable in the evaluation of polycythemia. Firstly, measurement of red cell mass is unnecessary if the hemoglobin is higher than 18.5